1. Field of the Invention
The present invention relates to tire testing machines utilizing a flat belt for a simulated road surface.
2. Prior Art
In the prior art various tire testing machines have been advanced. The testing of tires utilizing a flat belt surface is described in one form in U.S. Pat. No. 3,977,243. In this patent a flat belt is mounted on drums or pulleys and is power driven. A large framework is utilized spanning the belt to provide for mounting a rotating wheel and tire on a steerable framework relative to the overhead bridge type frame. The tire can be raised and lowered with respect to the upper reach of the driven belt, and thus loaded, while the tire is adjusted for camber and moved to simulate steering action. The unit further includes separate drive means for the belt and for the wheel and tire so that a slippage test can be conducted with a known amount of slip between the two surfaces. Control apparatus is provided in U.S. Pat. No. 3,977,243, and the parameters which normally are being tested are explained. However, the unit relies upon a relatively large bridge type framework for obtaining the necessary rigidity, and the belt mounting apparatus provides for a substantial span of belt between drums which makes it difficult for controlling the belt under lateral loads from camber, steering or tire asymmetry.
A compensating belt stabilizing apparatus which is for a tire testing machine is shown in U.S. Pat. No. 4,023,426. This device provides for a structure intended to compensate for forces imparted to the belt during tire testing.
Another type of road simulator facility is shown in U.S. Pat. No. 3,520,180 which utilizes a flat belt to simulate a roadway, but is made so that an entire vehicle can be mounted in position on the simulated roadways for testing the tires and other parts of the vehicle in place.
Further, Calspan Corporation, of Buffalo, N.Y., has published documents about its work in tire research, as outlined in the Society of Automotive Engineers Publication, "The Calspan Tire Research Facility: Design, Development and Initial Test Results" by K. D. Bird and J. F. Martin, Publication No. 730582 of the Society of Automotive Engineers, Inc., at that time of 2 Pennsylvania Plaza, New York, N.Y. 10001. The SAE is believed to now be at the address of 400 Commonwealth Drive, Warrendale, Pa. 15096. The facility includes large overhead framework for mounting a tire so that it can be moved into engagement with a belt simulating a roadway and can be cambered and steered as shown in the report, and in particular FIG. 1.
Calspan also has put out a brochure relating to this device entitled "TRIF In The Making", their No. D78474-3C which provides background information on various flat belt tire testers. As can be seen, in addition to using belts, there were devices that provided for testing tires on a parent vehicle, with the test apparatus supported by the vehicle, and also model tire testers were made utilizing flat belts mounted on a pair of large pulleys with overhead supports, again, for mounting the tire so that it would engage the flat belt. A further device advanced by Akron Standard, Machinery Division, of Akron, Ohio, their Specification No. 108-340-102 shows a drawing of a tire tester which utilizes a flat belt for simulating a roadway, and a support spindle that is mounted onto a relatively large frame using vertical ways that are offset from the belt.
In all of the devices, without the use of an overhead spanning bridge type frame, there are substantial moments that can be generated in supporting devices, and when the bridge type frames have been utilized, adjustments have been a problem, as well as obtaining proper control of the forces that are put into the tire. Further, it has been a problem to keep the belt mounting structure rigid enough to provide adequate control and support for the belt.
The Society of Automotive Engineers, Inc., Publication No. 780635 is a paper presented at the 1978 Passenger Car Meeting, June 5-9, 1978 and relates to the development of a flat surface tire rolling resistance facility at General Motors Corporation. This publication shows photographs of a unit which provides for a belt that can be driven, having a tire support frame that is positioned to the side of the belt so that the tire is cantilevered out from the frame, and thus involves moment loads on the frame.
Further, it has been necessary in most of the tire testers utilizing a flexible type belt for a simulated roadway to crown the drums mounting the belt to keep the belt tracking properly when it is subjected to loads such as a steering or camber load from a tire which tends to shift the belt from one side of the drums to the other.
Another problem is maintaining adequate stiffness in the supporting members for the belt drums.
Rolling drum type tire testers, where the tire is loaded directly against a rotary drum, are exemplified by U.S. Pat. No. 3,797,306.